From d9784148cb36f01966e689dbe6927350a0d31e7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B8ger=20Hanseg=C3=A5rd?= <joger.hansegard@qt.io>
Date: Sun, 5 Nov 2023 13:36:32 +0100
Subject: [PATCH] Remove ambiguity in handling of registry keys from setupAPI.h
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QWindowsScreen uses setupAPI.h's SetupDiOpenDevRegKey function to read
EDID data for monitors. This function is documented as returning
INVALID_HANDLE_VALUE in case of failure.

The QWindowsScreen code was ambiguous in the sense that it considered
both nullptr and INVALID_HANDLE_VALUE as being invalid handle values.
This inconsistency is likely not a bug, but makes the code harder to
understand.

This patch removes this ambiguity, and QWindowsScreen now follows the
documented behavior when SetupDiOpenDevRegKey fails. In addition, we
replace use of unique_ptr with the new QUniqueHandle template class
because HKEY is a handle type, not a regular pointer type.

Pick-to: 6.5
Change-Id: Ia863bda504077e59833f6f7a0f855e7915e4edd9
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit 55141c59cdc9144cd3aa9f5085df9db523f54736)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 .../platforms/windows/qwindowsscreen.cpp      | 21 ++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/plugins/platforms/windows/qwindowsscreen.cpp b/src/plugins/platforms/windows/qwindowsscreen.cpp
index 15c5aac8e35..a50f9fd4b05 100644
--- a/src/plugins/platforms/windows/qwindowsscreen.cpp
+++ b/src/plugins/platforms/windows/qwindowsscreen.cpp
@@ -19,6 +19,7 @@
 #include <private/qhighdpiscaling_p.h>
 #include <private/qwindowsfontdatabasebase_p.h>
 #include <private/qpixmap_win_p.h>
+#include <private/quniquehandle_p.h>
 
 #include <QtGui/qscreen.h>
 
@@ -116,16 +117,22 @@ static float getMonitorSDRWhiteLevel(DISPLAYCONFIG_PATH_TARGET_INFO *targetInfo)
 
 using WindowsScreenDataList = QList<QWindowsScreenData>;
 
-struct RegistryHandleDeleter
+namespace {
+
+struct DiRegKeyHandleTraits
 {
-    void operator()(HKEY handle) const noexcept
+    using Type = HKEY;
+    static Type invalidValue()
     {
-        if (handle != nullptr && handle != INVALID_HANDLE_VALUE)
-            RegCloseKey(handle);
+        // The setupapi.h functions return INVALID_HANDLE_VALUE when failing to open a registry key
+        return reinterpret_cast<HKEY>(INVALID_HANDLE_VALUE);
     }
+    static bool close(Type handle) { return RegCloseKey(handle) == ERROR_SUCCESS; }
 };
 
-using RegistryHandlePtr = std::unique_ptr<std::remove_pointer_t<HKEY>, RegistryHandleDeleter>;
+using DiRegKeyHandle = QUniqueHandle<DiRegKeyHandleTraits>;
+
+}
 
 static void setMonitorDataFromSetupApi(QWindowsScreenData &data,
                                        const std::vector<DISPLAYCONFIG_PATH_INFO> &pathGroup)
@@ -207,10 +214,10 @@ static void setMonitorDataFromSetupApi(QWindowsScreenData &data,
             continue;
         }
 
-        const RegistryHandlePtr edidRegistryKey{ SetupDiOpenDevRegKey(
+        const DiRegKeyHandle edidRegistryKey{ SetupDiOpenDevRegKey(
                 devInfo, &deviceInfoData, DICS_FLAG_GLOBAL, 0, DIREG_DEV, KEY_READ) };
 
-        if (!edidRegistryKey || edidRegistryKey.get() == INVALID_HANDLE_VALUE)
+        if (!edidRegistryKey.isValid())
             continue;
 
         DWORD edidDataSize{ 0 };